Internal combustion engines are increasingly fabricated using lightweight metals such as aluminum to decrease weight and achieve greater fuel efficiency. In particular, aluminum cylinder blocks have recently been fabricated with the internal surfaces of the cylinder bores spray coated with a material which acts to lubricate the cylinder bore and which aids the disposal of the engine's exhaust gases, for example, by catalyzing chemical reactions associated with the combustion process.
When the inner surface of a cylinder bore of a liner-less aluminum cylinder block is spray-coated, it is generally necessary to roughen the inner surface of the cylinder bore beforehand to enhance the adhesion of the spray coating. Surface roughening may be achieved, for example, using bead blasting, high pressure water jet blasting, or mechanical machining methods. However, these methods may not lead to a uniformly roughened surface, which can lead to adhesion failure of the coating to the cylinder wall. In addition, conventional machining methods can be time intensive and expensive, often requiring multiple pass machining steps to produce a cylinder bore surface having sufficient roughness to adhere the thermally sprayed coating.
Thus, a more reproducible and cost effective surface roughening method has been sought. The art continually searches for new methods of surface roughening, particularly roughening of cylindrical metal surfaces useful in fabricating internal combustion engines.